This invention relates to shielding devices for containers of radioactive materials and more particularly for devices used during the handling and measuring of material emitting high energy electromagnetic and/or particulate radiation such as gamma or beta radiation.
Because of the high energy of the radiation from materials presently used in radiation therapy and diagnosis, it is necessary to enclose such materials within radiation attenuating shields.
At present, for example, a commonly used radiation material is Technetium 99m (.sup.99m Tc) which is a strong gamma-radiating source. The material is routinely used in solution and is administered by hypodermic injection. Because of the high energies of the radiation of the material it is necessary to protect the personnel handling and administering these solutions. Such personnel require protection since they are repeatedly exposed to the radiation during the preparation of the solutions, the standardization procedures, dosage division and measurement and during administration. It is known to provide tubular shielding holders for the usual cylindrical containers of the radioactive materials. U.S. Pat. No. 3,820,541 shows such a holder for a hypodermic syringe. Such holders have the disadvantage of not permitting viewing of the contents of the containers and thus preclude direct measurement by observation or the ability to both observe and manually control the manipulation of the solutions during preparation, transfer to vials, standardization and dosage measurement into hypodermic syringes.
Recently these tubular shielded holders have been modified, as taught in U.S. Pat. No. 3,596,659 and its continuation-in-part U.S. Pat. No. 3,673,411 by utilizing an opening in the cylindrical shield to permit visual observation of the scales on the hypodermic syringe (U.S. Pat. No. 3,596,659) or the contents of multiple dose containers (U.S. Pat. No. 3,673,411). This opening in the shield is filled with a high density lead glass to attenuate the radiation escaping through the opening. While this permits observation for the manipulation and measurement of the contents of the container in the holder, one disadvantage is that even using the highest density lead glass window available, the attenuated radiation which still emanates from the shielded holder through this viewing glass is high enough to provide a potential hazard particularly to the eyes of personnel engaged in measuring operations as they must position their eyes directly in the line of the emanating radiation in order to reduce parallax errors and to the fingers and hands from such radiation through the windows when the shield is being held. This disadvantage is even more pronounced when used with other higher energy radiation materials requiring shielding during handling such as 131.sub.I, 67.sub.Ga and 80m.sub.Br as well as positron annhilation radiation emitters such as the cyclotron generated positron emitting isotopes of Carbon, Nitrogen and Oxygen.
Also commonly or experimentally used are the radioactive isotopes of thallium and rubidium and the standards such as 137.sub.Cs.
Another disadvantage is that the leaded glass is easily broken. Further, the shield is heavy and thus has disadvantages during use.
The March, 1952 issue of Nucleonics shows a shielded syringe having a shielding jacket surrounding a syringe with a thin lengthwise slit in the jacket for observation of the scale on the syringe by means of a mirror held apart and opposite from the slit. Illumination to permit viewing of the syringe is provided by an electric light inside the device. The device shown is heavy and bulky and is mounted to a base member for holding the remote syringe. This inherent bulkiness of the device combined with the facts tht the light for illuminating the syringe must be connected to a power source and that no shielding is provided between the shielding jacket and mirror and behind the mirror, prevents the device from being utilized as a hand-held device for administering small doses of radioactive material. This latter point is significant as a syringe must be raised to eye level to read accurately the scale markings on a syringe. This raises serious health problems for a user as the effects of exposure to radiation are cumulative and especially so in the region of the eyes. In addition, the device includes a long length of tubing which is unshielded between the device and needle.
Accordingly, it would be desirable to provide a shielding device which would offer maximum protection from radiation yet be suitable for hand-held direct dispensing of small dosages of radioactive material.